1. Field of the Invention
The present invention relates to the art of electrical connectors, and more particularly to a land grid array (LGA) connector assembly provided for mechanically and electrically connecting the LGA chip to a printed circuit board (PCB).
2. Description of the Prior Art
LGA electrical connectors are widely used in the connector industry for electrically connecting LGA chips to printed circuit boards (PCBs) in personal computers (PCs). Conventionally, an LGA connector mainly comprises an insulative housing, a multiplicity of terminals received therein, a load plate and a cam lever pivotably mounted on two opposite sides of the housing. The housing defines a multiplicity of terminal passageways in a rectangular array, for interferentially receiving corresponding terminals. Due to the very high density of leads arranged on an LGA chip, the LGA chip needs to be precisely seated on the LGA connector. Thus it is difficult to ensure reliable signal transmission between the terminals and the LGA chip.
Referring to FIGS. 4–6, a conventional land grid array connector assembly 8 comprises an insulative housing 82, a plurality of terminals 81 received in the housing 82, a metal stiffener 83 partly covering and reinforcing the housing 82, a load plate 84 pivotably received in an end of the stiffener 83, and a cam lever 85 pivotably mounted to an opposite end of the stiffener 83 for engaging with the cam lever 85. The housing 82 defines four sidewalls 820 and a central cavity disposed between the sidewalls 820. The central cavity is used for receiving a land grid array (LGA) chip 100 therein. A distal end of the terminal 81 is formed outward from a top surface of the central cavity, for being pressed to engage with a corresponding lead of the LGA chip 100. The load plate 84 comprises two opposite sides 840. A pair of pressing portions 841 is provided in respective middle portions of the sides 840, for pressing the LGA chip 100 engaging with the terminals 81. A pair of protrusions 821 is provided in respective opposite ends of the sidewalls 820. The protrusion 821 extends from an inner face of the sidewall 821 toward to the central cavity for securing the LGA chip 100 in the central cavity. When the LGA chip 100 engages with the connector assembly 8, the load plate 84 is rotated upward. The LGA chip 100 is placed in the central cavity of the housing 82. The load plate 84 is rotated from a vertical portion to a horizontal portion to make the two opposite sides 840 of the load plate 84 attach on corresponding sides of the LGA chip 100. The cam lever 85 is rotated to drive the load plate 84 to gradually approach the housing 82 until the pressing portions 841 of the sides 840 press the LGA chip 100 downwardly to make the leads of the LGA chip 100 contact with the distal ends of the terminals 81 and make the sides of the LGA chip 100 attach corresponding protrusions 821 and secure the LGA chip 100 in the protrusions 821 therebetween. As a result, mechanical and electrical engagement between the terminals 81 and corresponding leads (not shown) of the LGA chip 100 is attained.
However, because the protrusion 821 is formed at two ends of the sidewall 820, when the pressing portions 841 of the load plates 84 press on the LGA chip 100, the pressing force applied on the LGA chip 100 will generate friction at a junction of the sides of the LGA chip 100 engaged with the protrusions 821. The friction is prone to make the LGA chip 100 move upwardly relative to the housing 82 at a interface of the protrusion 821 and the side of the LGA chip 100 in vertical direction and spaces are formed between the leads of the LGA chip 100 and the terminals 81. As a result, the reliability of the mechanical and electrical engagement between the leads of the LGA chip 100 and the terminals 81 is decreased. If this happens, the LGA chip 100 can not be secured between the sidewalls reliably, and some terminals 81 are prone not to fully engage the corresponding leads of the LGA chip 100. Uniform engagement between the terminals 81 and the corresponding leads of the LGA chip 100 is destroyed, and even open electrical circuits are liable to establish therebetween. Thus, the reliability of the mechanical and electrical engagement between the terminals 81 and the corresponding leads of the LGA chip 100 is decreased.
Thus, there is a need to provide a new land grid connector assembly that overcomes the above-mentioned problems.